黄曲霉群菌种产生黄曲霉毒素B_1的调查研究

本文对来自我国20个省、市、自治区的不同基物上分离的和中国科学院微生物研究所菌种保藏室以及其他单位提供的黄曲霉群菌种,经随机选取82株进行了黄曲霉毒素B_1的测定,证明在测试的9个已知分类群中产生黄曲霉毒素B_1的菌种只限于寄生曲霉和黄曲霉,另外4株种名未定者也能产生此种毒素。在黄曲霉中产毒菌株约占30％(28.3％),其在GAN(葡萄糖硝酸铵)和大米培养基中的黄曲霉毒素B_1的最高产量分别为133,333.3和160,000.0ppb。总的来说,大体上可以反映在我国一般基物上黄曲霉产毒菌株存在的现状。在实验过程中,还对黄曲霉群菌种在GAN和大米培养基中黄曲霉毒素B_1的产量和产毒菌株数作了比较。发现在大米培养基中黄曲霉毒素B_1的产量高于GAN,而且测试的黄曲霉产毒菌株在这两种培养基中均各有不能产毒的菌株,因此,在测定产毒菌株时,若仅采用其中一种产毒培养基,往往会有漏掉产毒菌株的可能性。     

池塘中大肠埃希菌、柱状屈挠杆菌和鳗弧菌的动态演变规律的研究

目的:研究鱼池中不同生物体表面柱状屈挠杆菌、大肠埃希菌和鳗弧菌的区系分布.方法:通过对本中心渔场的鱼池中的几种主要病原菌进行定期采样测定.结果:这三种细菌在各种鱼体表的数量主要在102～104CFU/cm2波动,各种鱼体表上的同一细菌数量总体相差不大(几倍之间),但有一定的选择性;另外同一种鱼其体表上的各种细菌有相似的分布规律.研究还表明柱状屈挠杆菌、大肠埃希菌和鳗弧菌在池塘水体和各种浮游生物上的数量波动区域:浮游细菌为105～106CFU/L,大型浮游生物为103～104CFU/L,小型浮游生物为104～105CFU/L,其分布顺序(根据其平均值)都是:水体中的浮游细菌数量总是远远高于小型浮游生物(通常高10～100倍),小型浮游生物也总高于大型浮游生物(通常高10倍左右);同一种生物其体表上的各种病原菌有相同的分布规律.结论:这三种细菌在水体和各种生物体上的高峰期通常在5月下旬至6月上旬、7月下旬至8月上旬,因此,我们认为在这两个时间段,要特别重视,抓好防治鱼病的工作.     

黄曲霉群菌种产生黄曲霉毒素B1的调查研究

本文对来自我国20个省、市、自治区的不同基物上分离的和中国科学院微生物研究所菌种保藏室以及其他单位提供的黄曲霉群菌种,经随机选取82株进行了黄曲霉毒素B_1的测定,证明在测试的9个已知分类群中产生黄曲霉毒素B_1的菌种只限于寄生曲霉和黄曲霉,另外4株种名未定者也能产生此种毒素。在黄曲霉中产毒菌株约占30％(28.3％),其在GAN(葡萄糖硝酸铵)和大米培养基中的黄曲霉毒素B_1的最高产量分别为133,333.3和160,000.0ppb。总的来说,大体上可以反映在我国一般基物上黄曲霉产毒菌株存在的现状。在实验过程中,还对黄曲霉群菌种在GAN和大米培养基中黄曲霉毒素B_1的产量和产毒菌株数作了比较。发现在大米培养基中黄曲霉毒素B_1的产量高于GAN,而且测试的黄曲霉产毒菌株在这两种培养基中均各有不能产毒的菌株,因此,在测定产毒菌株时,若仅采用其中一种产毒培养基,往往会有漏掉产毒菌株的可能性。     

鱼类三种致病菌的粗脂多糖对异育银鲫的免疫原性

用温酚法从柱状嗜纤维菌、嗜水气单胞菌和鳗弧菌中提取的粗脂多糖（LPS）作为免疫原,分别接种异育银鲫后,通过测定受免鱼的交叉凝集抗体效价,头肾和血液中吞噬细胞的吞噬活性和用A.hydrophila活菌攻毒的方法,探讨鱼类3种致病菌的粗LPS对异育银鲫免疫原性的试验结果,结果表明,从3种致病菌中提取的粗LPS对异育银鲫均具有较强的免疫原性,受免鱼的血清中存在对3种致病菌的交叉凝集抗体;与对照鱼相比,头肾和血液中吞噬细胞的吞噬活性明显上升,受免鱼的A.hydrophila活菌攻毒均产生了较强的免疫保护力,说明在每种供试菌的粗LPS上都不同程度地存在3种致病菌的共同保护性抗原。     

翘嘴鳜烂鳃病病原的研究

从患典型烂鳃病的翘嘴鳜（Siniperca chuatisi）鳃上分离到6个菌株,从中筛选出毒性最强的SC-3,SC-6两菌株。通过生物学特性观察、生理生化特性分析和致病力测试的结果,认为SC-3、SC-6为柱状屈挠杆菌（Flexibacter columnaris）,是翘嘴鳜烂鳃病的病原菌。药物敏感试验表明,SC-3对多种抗生素、呋喃类药物敏感而对磺胺噻唑不敏感。     

Sensitive and rapid detection of Flavobacterium columnare in channel catfish Ictalurus punctatus by a loop-mediated isothermal amplification method

AIMS: To evaluate the loop-mediated isothermal amplification method (LAMP) for rapid detection of Flavobacterium columnare and determine the suitability of LAMP for rapid diagnosis of columnaris infection in channel catfish, Ictalurus punctatus. METHODS AND RESULTS: A set of four primers, two outer and two inner, were designed specifically to recognize 16S ribosomal RNA gene of this pathogen. Bacterial genomic DNA templates were prepared by hot lysis in a lysis buffer. Amplification of the specific gene segments was carried out at 65 degrees C for 1 h. The amplified gene products were analysed by agarose gel electrophoresis and detected by staining gels with ethidium bromide. A PCR assay was also included in this study. Our results demonstrate that the ladder-like pattern of bands from 204 bp specific to the Fl. columnare 16S ribosomal RNA gene was amplified. The detection limit of the LAMP assay was comparable to that of PCR in prepared genomic DNA reactions. In addition, this optimized LAMP assay was able to detect the Fl. columnare 16S ribosomal RNA gene in experimentally infected channel catfish. CONCLUSIONS: The LAMP assay for Fl. columnare detection in channel catfish was established. SIGNIFICANCE AND IMPACT OF THE STUDY: Because LAMP assay is a rapid, sensitive, specific, simple and cost-effective assay for Fl. columnare detection in channel catfish, it is useful for rapid diagnosis of Fl. columnare in fish hatcheries and the field.     

Computational characterization of epitopic region within the outer membrane protein candidate in Flavobacterium columnare for vaccine development

Abstract

Gram-negative bacteria is the main causative agents for columnaris disease outbreak to finfishes. The outer membrane proteins (OMPs) candidate of Flavobacterium columnare bacterial cell served a critical component for cellular invasion targeted to the eukaryotic cell and survival inside the macrophages. Therefore, OMPs considered as the supreme element for the development of promising vaccine against F. columnare. Implies advanced in silico approaches, the predicted 3-D model of targeted OMPs were characterized by the Swiss model server and validated through Procheck programs and Protein Structure Analysis (ProSA) web server. The protein sequences having B-cell binding sites were preferred from sequence alignment; afterwards the B cell epitopes prediction was prepared using the BCPred and amino acid pairs (AAP) prediction algorithms modules of BCPreds. Consequently, the selected antigenic amino acids sequences (B-cell epitopic regions) were analyzed for T-cell epitopes determination (MHC I and MHC II alleles binding sequence) performing the ProPred 1 and ProPred server respectively. The epitopes (9 mer: IKKYEPAPV, YGPNYKWKF and YRGLNVGTS) within the OMPs binds to both of the MHC classes (MHC I and MHC II) and covered highest number of MHC alleles are characterized. OMPs of F. columnare being conserved across serotypes and highly immunogenic for their exposed epitopes on the cell surface as a potent candidate focus to vaccine development for combating the disease problems in commercial aquaculture. The portrayed epitopes might be beneficial for practical designing of abundant peptide-based vaccine development against the columnaris through boosting up the advantageous immune responses.

Communicated by Ramaswamy H. Sarma